The present invention is related to a wireless (radio) communication apparatus for performing a mobile communication in a portable telephone, related to a transmission power control method used in this wireless communication apparatus, and also related to a recording medium for recording thereon a program used to execute the transmission power control method.
In general, mobile communication appliances such as portable telephone units are equipped with functions capable of controlling transmission power of own units based upon distances between base stations and mobile stations while information is transmitted. In the multiple access type communication system for multiplexing a plurality of communication channels at the same frequency, a transmission power control for controlling power of a signal reached to a base station at a necessary minimum value is necessarily required in order to increase a frequency utilization efficiency, depending upon interference power amounts between communication channels.
More specifically, in a CDMA (Code Division Multiple Access) type mobile communication appliance with employing a spread spectrum technique, there are great possibilities that a signal having low transmission power is masked by a signal having high transmission power, namely a so-called xe2x80x9cfar/near problemxe2x80x9d occurs. To solve such a problem, conventionally, the transmission power control with a high linearity and a wide dynamic range (for instance, 70 to 80 dB) is required. In the wide-band CDMA (W-CDMA), higher precision of the transmission power is required when signals having high power are transmitted, and thus, higher precision of the transmission power controls is further required. This wide-band CDMA system has been considered as the mobile communication system for the next generation.
As described above, in such a case that the mobile station is located in the vicinity of the base station in the system operation of the above wireless communication apparatus, there is a certain possibility that the transmission power of both the mobile station and the base station is lowered by way of the transmission power control. At the same time, the power consumption of the transmitter can be reduced by controlling the current consumption of the power amplifier.
However, in the above-described conventional wireless communication apparatus, when the current consumption control for the power amplifier is realized by the bias current control and the like, there is a variation in the gains caused by changing the biasing point. As a result, since the high-linearity power control corresponding to the system requirement condition can be hardly carried out, generally speaking, the power amplifier is used under the fixed biasing control.
As a consequence, in order to reduce the power consumption of the transmitter while realizing the high-linearity power control, there is a limitation in the conventional wireless communication apparatus such that the current consumption of the power amplifier operated under low output is lowered. In particular, the low power consumption of the transmitter may constitute a major subject in view of extension of communication available time of a mobile station.
The present invention has been made to solve the above-described problems of the prior art, and therefore, has an object to provide a wireless communication apparatus, a transmission power control method used in the wireless communication apparatus, and a recording medium, capable of securing absolute precision of required transmission power (i.e., allowable error with respect to power control target value), and furthermore, capable of realizing a high-linearity transmission power control with a wide dynamic range, while reducing power consumption of an electronic appliance by adjusting a current consumption of a power amplifier operated under low output power.
To achieve the above-described object, a wireless communication apparatus according to the present invention comprises: transmission power designating means for designating transmission power of a transmission signal to be transmitted from the wireless communication apparatus; controlling reference value producing means for producing a reference value used to control transmission power based upon the designated transmission power; timing control means for defining control timing of the transmission power; error detecting means for detecting an error based upon a difference value between a detection value obtained by detecting the transmission signal of the wireless communication apparatus and a detection value of a transmission signal when the transmission signal is transmitted under the designated transmission power; gain multiplying means for multiplying the detected error by a predetermined gain to obtain a correction value; control amount producing means for producing a feedback control amount based upon the correction value; power adjusting means for again setting a gain in a transmission power amplification at the control timing based upon the reference value for controlling the transmission power and the feedback control amount so as to adjust the transmission power; power amplifying means for power-amplifying the transmission signal; current consumption adjusting means for adjusting a current consumption in such a manner that a bias voltage is applied to the power amplifying means in response to the designated transmission power so as to control a bias current in the power amplifying means; and gain variation compensating means for compensating a variation in gains when the variation of the gains occurs in the transmission power amplification by controlling the bias current.
Also, in the wireless communication apparatus as above mentioned, the gain variation compensating means includes gain adjusting means for adjusting both the reference value used to control the transmission power and the gain control value based on the feedback control amount in response to the designated transmission power in the power adjusting means.
Also, the wireless communication apparatus as above mentioned, the gain variation compensating means includes compensation amount producing means for producing a gain variation compensation amount in response to the designated transmission power; and variable gain means for varying a gain based upon the gain variation compensation amount at output means of the power adjusting means.
Also, the wireless communication apparatus as above mentioned, the gain variation compensating means includes compensation amount producing means for producing a gain variation compensation amount in response to the designated transmission power; and signal amplitude varying means for varying a signal amplitude of the transmission signal based on the gain variation compensation amount.
A transmission power control method used in a wireless communication apparatus, according to the present invention comprises: a transmission power designating step for designating transmission power of a transmission signal to be transmitted from the wireless communication apparatus; a controlling reference value producing step for producing a reference value used to control transmission power based upon the designated transmission power; a timing control step for defining control timing of the transmission power; an error detecting step for detecting an error based upon a difference value between a detection value obtained by detecting the transmission signal of the wireless communication apparatus and a detection value of a transmission signal when the transmission signal is transmitted under the designated transmission power; a gain multiplying step for multiplying the detected error by a predetermined gain to obtain a correction value; a control amount producing step for producing a feedback control amount based upon the correction value; a power adjusting step for again setting a gain in a transmission power amplification at the control timing based upon the reference value for controlling the transmission power and the feedback control amount so as to adjust the transmission power; a power amplifying step for power-amplifying the transmission signal; a current consumption adjusting step for adjusting a current consumption in such a manner that a bias voltage is applied in response to the designated transmission power so as to control a bias current in the power amplifying step; and a gain variation compensating step for compensating a variation in gains when the variation of the gains occurs in the transmission power amplification by controlling the bias current.
Also, the transmission power control method as described above, the gain variation compensating step includes a gain adjusting step for adjusting both the reference value used to control the transmission power and the gain control value based on the feedback control amount in response to the designated transmission power in the power adjusting step.
Also, the transmission power control method as described above, the gain variation compensating step includes a compensation amount producing step for producing a gain variation compensation amount in response to the designated transmission power; and a variable gain step for varying a gain based upon the gain variation compensation amount at an output of the power adjusting step.
Also, the transmission power control method as above described, the gain variation compensating step includes a compensation amount producing step for producing a gain variation compensation amount in response to the designated transmission power; and a signal amplitude varying step for varying a signal amplitude of the transmission signal based on the gain variation compensation amount.
A recording medium readable by a computer, according to the present invention, is featured for recording thereon the transmission power control method used in the wireless communication apparatus as a program executed by the computer.
According to the present invention, the error is detected based upon the difference value between the detection value obtained by detecting the transmission signal of the wireless communication apparatus and the detection value of the transmission signal when this transmission signal is transmitted under the designated transmission power to be transmitted. Then, this error is multiplied by a predetermined gain to obtain the correction value. Based on this correction value, the feedback control amount is produced. At this time, a preselected gain is preferably set in such a manner that the variation amount of the transmission power controlled based on the feedback control amount may be located within the allowable range required for the variation amount of the transmission power which is controlled based upon the reference value of the transmission power control produced based on the designated transmission power. Then, based on both this feedback control amount and the reference value of the transmission power control, the gain of the transmission power amplification is again set at preselected control timing so as to control the transmission power. As a consequence, since the transmission power is continuously controlled within the continuously required allowable range of the variation amount, the absolute precision of the predetermined transmission power can be maintained while maintaining the linearity of the transmission power control characteristic. Also, since the bias current in the power amplifying means (power amplifying step) is controlled in response to the designated transmission power, the current consumption may be adjusted, and furthermore, the gain variation in the transmission power amplification caused by controlling this bias current may be compensated. As a consequence, the bias current may be optimized in response to the designated transmission power. In particular, when the transmission output power is low, since the current consumption is reduced, the power consumption may be lowered. Also, in the case that the gain is varied due to this bias current control, this variation amount of the gain may be compensated.
Further, according to the present invention, both the reference value of the transmission power control and the gain control value based on the feedback control amount are adjusted by the power adjusting means (power adjusting step) in response to the designated transmission power. As a result, the gain variation caused by the bias current control may be properly compensated in accordance with the transmission output power.
Furthermore, according to the present invention, the gain variation compensation amount is produced in response to the designated transmission power, and the gain is varied at the output of the power adjusting means (power adjusting step) based upon this gain variation compensation amount. As a result, the gain variation caused by the bias current control may be properly compensated in response to the transmission output power.
Moreover, according to the present invention, the gain variation compensation amount is produced in response to the designated transmission power, and the amplitude of the transmission signal is varied based upon this gain variation compensation amount. As a result, the gain variation caused by the bias current control may be properly compensated in response to the transmission output power.